Electrically induced deposition of a paint comprising pigment and a polycarboxylic acid resin provides an effective means for placing a coating of uniform depth upon all exposed areas of metal articles, including those having recessed or irregularly shaped surfaces. This process is exemplified in the art by Gilchrist, U.S. Pat. No. 3,230,162.
Large scale coating operations require that the coating materials employed in such process provide a physically and chemically stable coating bath, i.e., a bath that will permit continuous or intermittent addition of replacement feed, provide a uniform, blemish-free film, and, when applied to articles subjected to outdoor exposure, a high level of corrosion protection after conventional treatment to effect heat curing.
Preferably, the coating material for use in this process is one that requires a minimum of electrical energy to provide a film of acceptable thickness in a minimum of time upon the most inaccessible and/or electrically shielded surfaces of the workpiece. The degree to which a given coating material possesses this characteristic in relation to other coating formulations under like conditions is termed the "throw" or "throwing power" of the formulation.